Automatic field map generation and off-resonance correction for projection reconstruction imaging.

A new projection reconstruction technique utilizes the oversampling of low spatial frequencies to estimate and correct for off-resonance effects. Interleaved spokes are acquired at one of two different echo times. From separated early-TE and late-TE raw data, two one-quarter resolution images are reconstructed and a one-quarter resolution field map is computed. Multifrequency reconstruction with all the data is then used to simultaneously correct for off-resonance and compensate for the difference in echo times. Resulting images obtained on phantoms and in vivo demonstrate significantly reduced off-resonance artifact without the acquisition of a separate field map.